Dudley Fire Ecology Flashcards
summarize our general knowledge of climate change
its already happening, its going to get worse, its going to cost us dearly, we can still do something about it
fire ecology
fire is common, fire is good, plants have adaptations to fire, humans have used fire to adapt their habitats, fire interacts with the global climate
has the number of wildfires increased or decreased
decreased
has the severity and number of acres destroyed by fires increased or decreased and why
increased due to hotter driver conditions that make blazes harder to contain
does fire destroy wilderness?
no, destroyed is the wrong word, burned does not mean destroyed, fire is healthy for ecosystems
components of fire
fuel, O2, ignition source
fire:
a rapid chemical oxidative reaction that generates light and heat and produces a variety of chemical products
why is dry cellulose better for burning
water evaporation is cooling
is a forest fire more similar to a candle or a bunsen burner
candle, only the exterior of the flame burns because it requires oxygen to diffuse from the atmosphere unlike a Bunsen burner which has oxygen mixed in the fuel
process of a forest fire:
- evaporation of highly volatile compounds
- more evaporation of highly volute compounds
- volatiles enter flame and burn at the interface of the atmosphere and flame or enter the lower oxygen interior
- pyrolysis of cellulose into volatiles and solid char
- products of vaporization and pyrolysis miss the flame and move directly into the atmosphere
pyrolysis
decomposition caused by high temperatures
simplified process of a forest fire
1 Pyrolysis of plant materials in the absence of oxygen producing solid biochar and volatiles
2 Combustion of volatile gases when they mix with oxygen
what are the dominant predictors of a wild fire
amount of fuel
dryness of fuel
where are fires most common
areas with medium productivity and dry seasons
how often do fires occur naturally
every 2-200 years depending on location and conditions
surface fire
burning of forest floor, burning shrubs bottoms of trees ex. prairie grassland fire
crown fire
aerial fuels, tops of trees burning, lots of biomass, takes more to get it burning but once it starts it is intense ex. lodgepole pine tree forest fire in canada
consequences of crown fires
intense fire creates its own weather systems, convection columns 10-12 km high, fire whirls, 10-12 times the amount of wind, forward bursts can be 30m wide and shoot 100m
pyrocumulus clouds
evaporating water from fire condenses into clouds, can produce rain and extinguished fire, can produce lightning and start more fire, can cause downdrafts causing the fire to unpredictably change direction
ground fire
slowest but most destructive fire, actual ground is on fire, biomass in the soil is burning, can last months and spread unnoticed ex. peatland fire in drained lakebed
patchy effect of real fires
a large scale fire may have a mosaic of ground, crown, and surface fires
C3 plants
C3 plants do normal photosynthesis. all plants have C3 photosynthesis
C4 plants
C4 plants do C3 and C4, C4 refers to the number of carbons in the intermediate sites of photosynthesis. C4 is a mechanism for concentrating carbon in the leaves by increasing carbon dioxide level near the leaves, C4 are very productive plants and are usually warm plants
C3 Vs C4
C3 wins at low temperatures and shade but C4 wins at high temperatures and high light
what vegetation is fire prone
grasslands, mediterranean scrublands, boreal forests (c4 and gymnosperm primarily)
what vegetation is NOT fire prone
broadleaf forest and tundra (C3 and angiosperms primarily)
what if there were no fires
less grassland, less C4, less boreal forest, no mediterranean shrub-land, more broadleaf forest, very different vegetation and biodiversity
what is the role of volatile compounds in fire
volatile gases are the fuel that burns; some volatile gases are produced by heat decomposition of cellulose
when is a fire called a ground fire
the organic soil burns
how are grasslands maintained
periodic burning maintains grassland, without fire they would not stay grassland, other vegetation would grow
do fires kill plants
cooler fires allow resprouting from undamaged plants, hot fires kill vegetation but create favourable seedbeds, the longer the plant is in a fire the more tissues will heat up and be killed
how do different parts of plants survive fire
leaves die quickly
aboveground stems and trunks may not die depending on insulation, thickness, water content
below ground plant material may not die unless the fire is very hot or lasts a long time
3 types of pine fire adaptations
fire tolerators: individuals survive fire
fire embracers: individual dies but seeds are dispersed and prosper
fire avoiders: not adapted to fire
serotiny
seed cones that don’t open until a fire heats them
grass stage of pine
meristems are low and more protected from surface fires
self pruning
fire tolerators lose lower branches to survive fire better
fire evolution
evolution of traits in response to fire frequency
in North America, policy has been to suppress fires. what is the predicted effect of fire suppression
fires that occur are hotter and more likely to be canopy fires
if we could totally suppress fire worldwide, the result would be a large increase in
broadleaf forest
in california, damage from fire was photographed showing melted cars sitting below undamaged trees. explain this
a surface fire occurred which burned hot and low burning matter on the surface including the cars but not burning the tops of trees
